A process described in Europe 442584 involves an asymmetrical transformation of amino acid amides with the aid of optically active carboxylic acids. The asymmetrical transformation of methionine amide with the aid of 2-pyrrolidone-5-carboxylic acid is mentioned as an example.
Although optically active methionine amide can be obtained with a large enantiomeric excess (ee), the described resolution of methionine amide has number of practical, yet significant drawbacks. In particular the crystal properties of the salt of methionine amide and 2-pyrrolidone-5-carboxylic acid formed as an intermediate are relatively poor. This necessarily results in relatively poor filterability and processability in general. Moreover, the 2-pyrrolidone-5-carboxylic acid is not easily recoverable.